I have actually swapped whole engine/trannies including subframe and front struts before. It is a fairly easy thing to do.
BIG WARNING: IF THERE ARE BOLTS BETWEEN THE TRANNY AND ENGINE (I.E. TORQUE CONVERTER) WHICH NEED TO BE ACCESSED THROUGH THE INSPECTION PLATE ON THE BOTTOM FRONT OF THE TRANNY, TAKE THEM OUT NOW!! I HAVEN'T WORKED ON AN AUTOMATIC 318, BUT PAST EXPERIENCE IS THAT THERE ARE FOUR BOLTS HOLDING THE TORQUE CONVERTER TO THE FLYWHEEL. IF YOU PULL THE TRANNY OFF WITHOUT TAKING THE TORQUE CONVERTER LOOSE FROM THE FLYWHEEL, YOU GET A MESS OF FLUID EVERYWHERE. ALSO YOU WONT HAVE ACCESS TO GET TO THESE BOLTS ONCE IT IS SITTING ON THE GROUND. You may be making the whole job too complex. I would do the following:
1) Make sure all other connections are clear (rear tranny mounts, wires, shifter linkage, tranny cooling lines, etc.)
2)Center your jack under the subframe and jack it up until you are supporting the weight
3) Put your moving dolly (Go to HarborFreight if you have one) or any other roll around/slide around item under the tranny. Most of the weight will end up on the jack anyway.
4) Unbolt the subframe and lower it all straight down.
5) Pull straight forward until you are clear of the car.
If you need to, you can use a second jack to tip the front of the car further up for clearence.
Just don't tip it off your jackstands!!!! After that, you can use the jack to drag it into the garage.
To get your jack back, move the eng/tran to where you want. Jack it up some and stack 2x4 under both ends of the subframe, then lower it down.
At this point, you can get a moving dolly or something if you want it to remain mobile. I don't know how much weight they hold. I'm not sure why you need it mobile. I would just strip off the tranny if you are selling seperate and leave them in place. The buyer will need a cherry picker to lift the engine anyway.
Hope this helps.